Bearing capacity test and stiffness research on CFRP strengthened existing reinforced concrete poles with joint

In order to reveal the bearing capacity and failure mechanism of CFRP strengthened existing reinforced concrete poles with corrosion steel collar joints, three poles from a road section of Southwest line in the Southern Power Grid were selected to conduct flexural capacity test research. Two pole specimens were pasted with double vertical CFRP and one pole specimen was pasted with single vertical CFRP. The whole process of forcing and failure mode of all specimens was observed by the test, and the important indicators, such as curves of load-deflection, curves of stiffness degeneration and ultimate bearing capacity, were obtained. Results indicated that the strengthened poles with connection joints were mainly bond failure between concrete and the external CFRP, the damage process is very fast, and the failure feature is brittle. These specimens' cross-sectional strains conform to the assumption of plane cross-section. Also, bearing capacity and stiffness of the strengthened specimens are much larger than those without CFRP. The bearing capacity of specimens pasted with double CFRPs is larger than that of the specimen with single CFRP. Comparing the initial stiffness and elastic-plastic stiffness, it is seen that the ones with double CFRPs are a little higher than the one with single CFRP. Weighting the cost-effective effect, it is determined that pasting single-layer CFRP longitudinally is more economical and reasonable. The results can provide a reference to the same type of existing reinforced concrete poles for reinforcing design.